THE EFFECT OF DIFFERENT COUPLING AGENT ON ZEOLITE …umpir.ump.edu.my/4395/1/CD6350_NIK_NUR_ZARNAYAH.pdf · 2015. 3. 3. · For zeolite surface modification, usually use silane coupling

THE EFFECT OF DIFFERENT COUPLING AGENT ON ZEOLITE

MODIFICATION FOR DEVELOPMENT OF POLYETEHERSULFONE MMMs FOR

O2/N2 SEPARATION.

NIK NUR ZANARYAH BINTI NIK HASSAN

Thesis submitted in fulfillment of the requirements

For the award of the degree of

Bachelor of Chemical Engineering (Gas Technology)

Faculty of Chemical Engineering and Natural Resources

UNIVERSITI MALAYSIA PAHANG

JANUARY 2012

vi

ABSTRACT

The industrial gas separations have been attracted in using membrane for gas

separations since membrane separation technologies have the advantages of energy

efficiency, simplicity and low cost. This lead to the exploration mixed matrix membrane

(MMMs) that combining the polymeric membrane filled with organics particles. In

order to improve the interaction between polymer and zeolite, chemical modification on

the surface of zeolite using silane coupling agents need to be done to increase the

compatibility between zeolite and polymer. In this study, the effect of difference

coupling agents used on zeolite modification in development of Polyethersulfone

MMMs for O2/N2 separation was studied. Three types of coupling agents were used

which are 3-aminopropyltriethoxysilane, glycidoxypropyltrimethoxysilane and 3-

aminopropyltrimethoxy- silane (APTMOS). The polymer solution was prepared

contains of 30% Polyethersulfone (PES) as the polymer, 55% of N-Methyl Pyrolidone

(NMP) as the solvent and 15% of zeolite 5A. The dry/wet phase inversion method was

used to produce the membrane. The membrane was coated with silicone and n-hexane

in order to decrease the surface defect and tested using O2 and N2 gases to determine the

membrane performance. For surface and cross section image of membrane were

identified using Scanning Electron Microscope (SEM). Membrane was also

characterized using Fourier Transform Infrared Spectroscopy (FTIR) to analyze the

presence of silane coupling agent functional group. As a conclusion, the best

performance was identified by using glycidoxypropyltrimethoxysilane which gives high

selectivity about 3.14.

vii

ABSTRAK

Industri pemisahan gas telah menarik minat menggunakan membran bagi

memisahkan gas. Antara kelebihan menggunakan teknologi membran adalah

penggunaan tenaga secara efisyen, mudah dan kos yang rendah. Ini membawa kepada

penerokaan campuran membran matrik yang menggabungkan membran polimer dengan

zeolit. Bagi meningkatkan keserasian antara polimer dan zeolit, pengubahsuaian

permukaan zeolit menggunakan ejen gabungan silan perlu dilakukan. Dalam kajian ini,

kesan penggunaan ejen gabungan silan yang berlainan dalam pengubahsuaian

permukaan zeolit untuk menghasilkan campuran membran matrik Poliethersulfona

(PES) bagi memisahkan oksigen dan nitrogen telah dikaji. Tiga jenis ejen gabungan

silana telah digunakan iaitu 3-aminopropyltriethosisilan, glycidosipropyltrimethosisilan

and 3-aminopropyltrimethosisilan. Campuran polimer yang mengandungi 30%

Poliethersulfona (PES) sebagai polimer, 55% N-MetilPyrolidona (NMP) sebagai bahan

pelarut dan 15% zeolit 5A telah disediakan. Untuk menghasilkan membran ini proses

fasa balikan kering/basah telah digunakan. Membran yang terhasil akan disalut dengan

silikon dan N-Heksana untuk tujuan mengurangkan kecacatan pada permukaan

membran. Membran yang terhasil diuji dengan menggunakan gas oksigen dan nitrogen.

Permukaan dan imej keratan rentas membran telah dikaji menggunakan Mikroskop

Pengimbas Elektron (SEM). Membran telah dianalisa menggunakan Spektroskopi Infra-

Merah Fourier (FTIR) untuk mengkaji kehadiran kumpulan ejen gabungan silana. Dapat

diputuskan bahawa penggunaan glycidosipropyltrimethosisilan memberi kadar

pemilihan yang paling tinggi iaitu sebanyak 3.14.

viii

TABLE OF CONTENTS

Page

SUPERVISOR’S DECLARATION ii

STUDENTS’S DECLARATION iii

DEDICATION iv

ACKNOWLEDGMENT v

ABSTRACT vi

ABSTRAK vii

TABLE OF CONTENTS viii

LIST OF TABLES xi

LIST OF FIGURES xii

LIST OF SYMBOLS xiv

LIST OF ABBREVIATIONS xv

CHAPTER 1 INTRODUCTION 1

1.1 Research background 1

1.2 Problem Statement 3

1.3 Objectives 4

1.4 Scope of study 4

1.5 Rational and Significance 5

CHAPTER 2 LITERATURE REVIEW 6

2.1 Historical Background of membranes 6

2.2 Membrane Separation Technology 8

2.3 Mechanism for gas separation 9

2.4 Mixed matrix membrane 11

2.5 Zeolite surface modification 14

2.5.1 Zeolite 14 2.5.2 Non-idealities in mixed matrix membranes (MMMs) 16 2.5.3 Zeolite surface modification 18

ix

CHAPTER 3 METHODOLOGY 20

3.1 Material 20

3.1.1 Polyethersulfone 20 3.1.2 N-methyl-2-Pyrolidone (NMP) 21 3.1.3 Properties of coagulation medium 21 3.1.4 Zeolite 5A 22 3.1.5 Properties of substances for zeolite modification 22 3.1.5.1 3-aminopropyl-trimethoxysilane (APTMOS) 23 3.1.5.2 3-aminopropyl-triethoxysilane (APTES) 23 3.1.5.3 Glycidoxypropyl-trimethoxysilane (GPTMS) 24 3.1.5.4 Ethanol 24 3.1.5.5 Distilled water 25

3.2 Research Design 26

3.3 Preparation of modification zeolite 27

3.4 Preparation of dope solution 27

3.5 Membrane casting 28

3.6 Membrane coating 29

3.7 Gas permeation test 29

3.8 Membrane characterization 30

3.8.1 Scanning Electron Microscopic (SEM) 30 3.8.2 Fourier Transform Infrared Spectroscopy (FTIR) 31

CHAPTER 4 RESULTS AND DISCUSSIONS 32

4.1 Effect of different coupling agents on the permeability 33

and selectivity of MMMs

4.2 FTIR analysis for different mixed matrix membrane with 37

different coupling agents

4.2 Effect of Different Coupling Agents on Zeolite 40

Modification on Morphology of Coated PES MMMS

4.3 Effect of Pressure on Selectivity and Permeability of MMMs 43

x

CHAPTER 5 CONCLUSIONS AND RECOMMENDATIONS 48

5.1 Conclusions 48

5.2 Recommendations 50

REFERENCES 51

APPENDICES 54

xi

LIST OF TABLES

Table No. Title Page

2.1 Events of the development of membrane 7

technology 2.2 Properties of zeolite 15

3.1 Properties of N-methyl-2-Pyrolidone (NMP) 21

3.2 Properties of coagulation medium 21

3.3 Properties of zeolite 5A 22

3.4 Properties of 3-aminopropyl-trimethoxysilane 23 3.5 Properties of 3-aminopropyl-triethoxysilane 23

3.6 Properties of Glycidoxypropyl-trimethoxysilane 24 3.7 Properties of ethanol 24

3.8 Properties of distilled water 25

4.1 Concentrations of materials for dope solution 32

formulation

4.2 Average separation properties of modified MMMs 34 using different coupling agents at 3 bars

4.3 Average separation properties of coated MMMs at 44

different pressure

xii

LIST OF FIGURES

Figure No. Titles Page 2.1 Asymmetric membrane structure 9 2.2 Mechanism for permeation of gases through 10

membranes

2.3 Illustration of gas molecules’ diffusion through a 11 molecular sieve material

2.4 Relationship between the O2/N2 selectivity and O2 12

permeability for polymeric membranes and inorganic membranes

2.5 Gas permeation through mixed matrix membranes 13

containing different amounts of dispersed zeolite particles

2.6 The tetrahedral molecular structure of zeolite 5A 15 2.7 Illustration of morphologies and gas transport 16

properties of non-idealities in mixed matrix membrane

2.8 Hydrolysis reaction of silane coupling agents 18

2.9 Reaction of the chemical modification of zeolite 18 surface

3.1 Dope solution preparation 28

3.2 Manual hand casting 29

3.3 Gas permeation unit 30

3.4 Scanning Electron Microscopic (SEM) 30

4.1 Pressure normalized flux and selectivity at different 35

solution at 3bars 4.2 Voids between polymer and zeolite for S1 36 4.3 Voids between polymer and zeolite for S2 36 4.4 Voids between polymer and zeolite for S3 37 4.5 FTIR spectra recorded for S1 38

xiii

4.6 FTIR spectra recorded for S2 38 4.7 FTIR spectra recorded for S3 39 4.8 Coated surface at S1 MMMs 40

4.9 Coated surface at S2 MMMs 41

4.10 Coated surface at S3 MMMs 41 4.11 Cross section of MMMs for S1 42 4.12 Cross section of MMMs for S2 42 4.13 Cross section of MMMs for S3 43 4.14 Pressure-normalized flux and selectivity of coated 45

MMMs of S1

4.15 Pressure-normalized flux and selectivity of coated 45 MMMs of S2

4.16 Pressure-normalized flux and selectivity of coated 46

MMMs of S3

xiv

LIST OF SYMBOLS

P Overall permeability Pc Permeability of the continuous polymer phase Pd Permeability of the dispersed zeolite phase Ø Volume fraction α Selectivity (Unitless) Q Flow rate of gas species A Area of membrane ∆� Pressure difference across membrane (cm Hg) Å Amstrong nm Nanometer µm Micrometer cm Centimeter mL Milliliter % Percentage Kg Kilogram g Gram °C Degree celcius K Kelvin F Fahrenheit kPa Kilopascal (P/l) Pressure Normalized Flux (cm3 (STP)/ cm2. s. cmHg)

xv

LIST OF ABBREVIATIONS

CMS Carbon molecular sieves O2 Oxygen N2 Nitrogen wt% Weight percentage PES Polyethersulfone MMMs Mixed Matrix Membranes APTES 3-aminopropyltriethoxysilane GPTMS Glycidoxypropyltrimethoxysilane APTMOS 3-aminopropyltrimethoxysilane SEM Scanning Electron Microscopic STP Standard Pressure and Temperature GPU Gas Permeation Unit AlO4 Aluminium Oxide SiO4 Silicone Oxide NMP N-methyl-2-Pyrolidone H2O Water PDMS Polydimethylsiloxane FTIR Fourier Transform Infrared Spectroscop

CHAPTER 1

INTRODUCTION

1.1 Research Background

During the past 20 years, gas separation has become main industrial application

of membrane technology (Baker, 2004). Gas separation is an important unit operation

and widely use in chemical industries. For examples the separation of air into oxygen

and nitrogen and the removal of volatile organic compounds from effluent streams. The

traditional method that use for gas separation include cryogenic distillation and

adsorbent bed process. Recently, membrane based gas separation has been used (Javaid,

2005).

Membrane based gas separation widely used due to its inherent advantages

compare to traditional method, low capital and operating costs, lower energy

requirements and ease of operation (Chung et al., 2007). Membrane based process has

been used in wide array of application such as microfiltration, ultrafiltration,

nanofiltration, reverse osmosis and electrodialysis. There are some limitations for

polymer membrane which are poor contaminant resistance, low chemical and thermal

stability. In addition polymer membrane materials reached a limit in the tradeoff

between productivity and selectivity (Kulprathipanja, 2010).

2

Then research is focused on forming novel membranes such as nanoporous

molecular sieving material. Example of nanoporous molecular sieving such as carbon

molecular sieves (CMS), silica and zeolite. The selectivity and permeability for carbon

membrane is higher than polymer membrane. In spite of these findings carbon

membrane not widely used in industrial separation process due to the inherent

brittleness of carbon material, high price and aging of the carbon surface by chemical

surface reaction ( Nunes and Peinemann, 2006).

Then mixed matrix membrane has been proposed as an alternative approach to

obtain high selectivity and permeability from molecular sieving membranes and

economical processing of polymer (Vu et al., 2003). The fragility inherent in organics

membrane can be avoided by using flexible polymer as continuous matrix. Mixed

matrix membrane is an organic –inorganic membrane consists of dispersed inorganics

particles such as zeolite particles in continuous organic polymer. Mixed matrix

membrane provide the advantages of both inorganic and organics membrane

(Kulprathipanja, 2010).

Zeolites also known as molecular sieves are crystalline aluminosilicates of group

IA and group IIA elements such as sodium, potassium, magnesium and calcium. The

development of a successful mixed matrix membrane depends on good match and

compatibility between zeolite and polymer material. There are some obstacles in

producing successful mixed matrix membrane which is poor adhesion between polymer

and zeolite particles which produce voids and defects in membrane. To overcome this

problem, coupling agents has been used to improve adhesion between zeolite and

polymer (Kulprathipanja, 2010).

For zeolite surface modification, usually use silane coupling agents such as 3-

aminopropyltriethoxysilane, 3-aminopropyl-trimethoxysilane, N-β-(aminoethyl)-γ-

aminopropyltrimethoxy silane, (γ - glycidyloxypropyl)-trimethoxy silane and (3-

aminopropyl)-dimethylethoxy silane. 3-aminopropyltriethoxysilane consists of three

ethoxy group and for 3-aminopropyl-trimethoxysilane it consists of three methoxy

group. Both of the coupling agents consist of amino functional group and for (γ -

glycidyloxypropyl)-trimethoxy silane it consists of epoxy functional group. Ethoxy and

3

methoxy group is a hydrozable group. Silanol group was produce through hydrolysis

reaction. The silanol groups will react with hydroxyl group found on zeolite surface to

form siloxane bonds through condensation reaction.

From a research on enhanced gas permeation performance of polyethersulfone

mixed matrix hollow fibre membranes using novel Dynasylan Ameo silane agent show

that with membrane with modified zeolite, gas separation performance higher compare

to membrane with unmodified zeolite. Selectivity of O2/N2 for untreated zeolite was

lowest compare to treated zeolite which is 2.13. For 10wt% of treated zeolite the

selectivity was 2.74, 15 wt % of treated zeolite the selectivity was 3.07 and 20 wt% of

treated zeolite the selectivity was 4.78. Therefore, by using coupling agents, it will

expect to increase the selectivity of gas separation. By using different coupling agents

give different selectivity of gas. For hollow fiber 3-aminopropyltriethoxysilane

selectivity of O2/N2 was 4.78 (Ismail et al., 2008). For 3-aminopropyltrimethoxsilane

the selectivity of O2/N2 was 3.25 (Hidayat, 2010).

1.2 Problem statement

Membrane separation process have widely use especially for gas and liquid

separations. Gas and liquids separation process required a membrane with high

permeability and selectivity. Currently, carbon molecular sieve and zeolite had been

embedded in polymer matrix due to their excellent separation performances for the

gases. In mixed matrix membranes fabrication, the most important thing is to ensure

there is a good contact between polymer matrix and zeolite.

For PES, it is widely used for gas separations due to the wide operating

temperature, limit, wide operating pH tolerances, fairly good chlorine resistance, easy

fabrication in wide variety of configuration and good chemical resistance to aliphatic

hydrocarbons, alcohol and acids. But in PES, there is disadvantage which is poor

compatibility between zeolite and polymer matrix. In this research, we need to study the

effect of different coupling agents on zeolite modification for PES MMMs in order to

obtain a good performance of membrane.

4

1.3 Objectives

Based on the problem statement, the objectives of this study are:

a) To develop Polyethersulfone Mixed Matrix Membranes for O2/N2 separation.

b) To study the effect of difference coupling agents used on zeolite modification in

development of Polyethersulfone Mixed Matrix Membranes for O2/N2 separation.

1.4 Scope of study

There are several scopes of study that have been outlined to achieve the

objectives of this study which are:

a) Three types of coupling agents were used which are 3-aminopropyltriethoxysilane

(APTES), glycidoxypropyltrimethoxysilane (GPTMS) and 3-

aminopropyltrimethoxy- silane (APTMOS).

b) Preparing asymmetric mixed matrix membrane by phase inversion technique using

dope solution contain of Polyethersulfone (polymer) and N-methyl-2-Pyrolidone

(solvent).

c) Characterize the membranes morphology using Scanning Electron Microscopy

(SEM).

d) Characterize the functional group in membranes using Fourier Transform Infrared

Spectroscopy (FTIR)

5

1.5 Rational and significance

To improve the interfacial strength to enhance the separation performance is to

use chemical modification of zeolite surface with coupling agent. Different coupling

agents have different effect on the voids between zeolite and polymer. The presence of

void at polymer- zeolite interface reducing the separation performance of the

membrane. By using coupling agents, the selectivity of gas will increase and can

achieve better gas separation. By achieve better gas separation, can save cost and

energy.

CHAPTER 2

LITERATURE REVIEW

2.1 Historical Background of membranes

Nowadays membrane gained an important place in chemical technology and

used widely like in hydrogen separation, oxygen-nitrogen separation, natural gas

separation, vapor-vapor separation and dehydration of air (Baker, 2006). The

development of membrane dates back to early 18th century and has been developing

rapidly. In 1784, Abbé Nolet started to use the word osmosis to describe permeation of

water through a diaphragm. At nineteenth and early twentieth century, membrane uses

limited at laboratory tools in developing physical and chemistry theories only (Baker

2006). Table 2.1 shows the events of the development of membrane technology.

7

Table 2.1: Events of the development of membrane technology.

Year/ century

Researcher Inventor

1748 Abbé Nolet

Introduced the word osmosis to describe water

permeation through water

1829 Thomas Graham Performed first recorded experiment on the transport

of gases and vapors in polymeric membranes

1855 Fick Proposed quantitative description of material transport

through boundary layer

1887 Van‟t Hoff Explain the behavior of ideal dilute solutions and

introduce Van‟t Hoff equation

Maxwell et al Develop Kinetic theory of gases

1907 Bechold Devised a technique in preparation nitrocellulose

membrane of graded pore size using a buble test

1930 Ekford, Zsigmondy,

Bachmann and

Ferry

Improved Bechhhold’s technique and microporous

colloidion membrane commercially available

1960 Loeb–Sourirajan Develop process for making defect free, high flux,

anisotropic reverse osmosis membranes.

1966 Alex Zaffaroni Use membranes technique to control drug delivery

system

1980 -Microfiltration, ultrafiltration, reverse osmosis and

electrodialysis widely established

-Monsanto Prism develops membrane for hydrogen

separation.

1980 GFT (German

engineering

company)

Introduce commercial pervaporation systems for

dehydration of alcohol

Source: Baker (2006)

8

2.2 Membrane Separation Technology

Membrane can be defined as a barrier which separates two phases and transport

of various chemicals in a selective manner (Ravanchi et al., 2009). Membrane can be

homogeneous or heterogeneous, symmetric or asymmetric in structure. Homogeneous is

completely uniform in composition and structure and heterogeneous consists of holes or

pores of finite dimensions or consisting if layered structured (Baker, 2006). Transport

through the membrane take place when there is driving force applied to the components

in the feed. In membrane processes, driving force can be defined as a pressure

difference or a concentration difference across the membrane. Another driving force is

electrical potential difference (Ravanchi et al., 2009).

The separation of gas mixture with membrane is rapidly growing and become

one of significant unit operations in the chemical industry (Nunes and Peinemann ,

2006). In membrane based gas separation, components separated from mixture by

differential permeation through membranes. There are some advantages of membrane

based technology such as low capital cost and high energy efficiency compare to older

technique like crygogenic distillation, absorption and adsorption (Chung et al., 2007).

The membrane performance for separations is characterized by permeability

across the membrane and selectivity. Selectivity can be defined as the ratio of

permeabilities of feed component across the membrane. Permeability and selectivity are

temperature dependent. For membrane mechanism, each feed component is sorbed by

the membrane at interface, transported by diffusion across membrane through the voids

between polymer chains and desorbed at other interface.

9

Membrane can be classified into two groups according to its morphology which

are symmetric and asymmetric. Symmetric membrane is film without pores. Symmetric

membrane significantly low permeability and hardly to practical uses. Asymmetric

membrane structure consists of dense skin layer and a porous support layer (Li et al.,

2008). Asymmetric membrane structure is shown in Figure 2.1. To maximize the

membrane productivity needs to minimize the thickness of the membrane selective skin

layer. Polymer membranes for gas separation have the geometry of an asymmetric flat

sheet, a thin film composite or an asymmetric hollow fibre. These membranes have

highly porous non- selective support layer and an ultrathin selective layer less than

100nm. Ultrathin selective layer provide membrane selectivity while highly porous non

selective provide membrane mechanical strength. The membrane with thinner selective

layer will have higher productivity compare to thicker layer (Kulprathipanja, 2010).

Figure 2.1: Asymmetric membrane structure

Sorce: Kulprathipanja (2010)

2.3 Mechanism for gas separation

There were various mechanisms for gas transports across membranes have been

proposed depending on the properties of permeant and the membrane. The mechanism

for gas separation is divided into porous membranes and dense membranes. The

10

mechanisms include Knudsen diffusion, the molecular sieve effects and a solution

diffusion mechanism. However, most of these models have been found to be applicable

only to a limited number of gas/material systems (Pandey and Chauhan, 2001). As a

practical material, solution diffusion based gas transport through membrane is used

exclusively in current commercial devices (Shu Shu, 2007). Figure 2.2 shows

mechanism for permeation of gases through membranes.

Figure 2.2: Mechanism for permeation of gases through membranes.

Source: Shu Shu (2007)

In molecular diffusion, the mean free path of the gas molecules is smaller than

the pore size. Diffusion occurs primarily through molecule-molecule collisions. In this

mechanism, the driving force is the composition gradient. If a pressure gradient is

applied in such pore regimes bulk (laminar) flow occurs, as given by Poiseuille flow or

viscous flow. For Knudson diffusion, the separation is based on gas molecules passing

through membrane pores small enough to prevent bulk diffusion. Separation is based on

the difference in the mean path of the gas molecules due to collisions with the pore

walls, which is related to the molecular weight (Javaid, 2005).

Molecular sieving relies on size exclusion to separate gas mixtures. Pores within

the membrane are of a carefully controlled size relative to the kinetic (sieving) diameter

of the gas molecule. This allows diffusion of smaller gases at a much faster rate than

larger gas molecules (Colin et al., 2008). The diffusion mechanism is illustrated in

11

Figure 2.3. Zeolites are able to discriminate even in size and shape which gives superb

gas separation efficiency. When one gas molecule is able to transverse the pore structure

while the other is precluded due to oversize, the selectivity could ideally reach infinity

(Shu Shu, 2007).

Figure 2.3: Illustration of gas molecule diffusion through a molecular sieve material

Source: Shu Shu (2007)

In dense membrane, solution diffusion widely accepted as mechanism of

transport. This mechanism consist three steps of process. For first step the gas

molecules are absorbed by the membrane surface on the upstream end. Second step was

followed by the diffusion of the gas molecules through the polymer matrix. Finally the

gas molecules evaporate on the downstream end (Javaid, 2005)

2.3 Mixed matrix membrane

During the last 2 decades, polymer based organic and inorganic get worldwide

attention due to the superior performance in term of mechanical toughness permeability

and selectivity for gas separation and photoconductivity for electronics. This concept

has been use for gas liquid separation membrane by combine organic and inorganic

material which called as mixed matrix membrane (Li et al., 2006). Mixed matrix

membrane can be defined as the hybrid membrane which consists of inorganic

molecular sieves (zeolite) and polymer. This membrane is a combination of selectivity

of zeolite membranes with the low cost and ease of manufacture of polymer

membranes. For performances of polymeric membranes in gas separation there is an

12

upper limit which predicted by Robeson in early 1990. Figure 2.4 shows the

performance of various membrane materials available for the separation of O2/N2.

Figure 2.4: Relationship between the O2/N2 selectivity and O2 permeability for

polymeric membranes and inorganic membranes

Source: Robeson (1991)

From Figure 2.4, it shows that for polymeric materials trade off exists between

permeability and selectivity with an upper-bound limit. For polymeric membrane, the

permeability and selectivity is tracking along this line instead of exceeding it. On the

other hand, the inorganic materials properties lying far beyond the upper bound limit.

The application of inorganic membrane is hindered by the lack of technology to form

continuous and defect free membranes, the extremely high cost for membrane

production and handling issue. A new approach is needed to provide cost effective

membrane with separation properties well above the upper bound limit. The latest

membrane with the potential for future applications is mixed matrix membrane

(MMMs) which consists of organic polymer and inorganic particle (Chung et al., 2007).

In the development of mixed matrix membrane, proper selection for polymer as

continuous phase and inorganics as dispersed phase properties is important which it can

affect membrane morphology and separation performance. Mixed matrix membranes

have higher selectivity compare to continuous polymer matrix. For MMMs fabrication

13

there were two inorganics phase material that have been use which are non porous and

porous filler. For porous filler, zeolite and carbon molecular sieves (CMS) were

commonly used. These materials have hydrophobic internal surface that used in industry

to separate air by adsorption of oxygen and remove carbon dioxide. The additional of

small volume fraction of zeolite to polymer matrix can increase the separation

efficiency (Aroon et al., 2010). At low loadings of zeolite, permeation occurs by

combination of diffusion through the polymer phase and diffusion through the

permeable zeolite particles. The concept is show in Figure 2.5.

Figure 2.5: Gas permeation through mixed matrix membranes containing different

amounts of dispersed zeolite particles

Source: Baker (2004)

At low loading of zeolite, the effect of permeable zeolite on permeation can be

expressed mathematically by the expression shown below which develop by Maxwell in

1870s. For the equation 2.1, P is the overall permeability of mixed matrix membrane

material, is the volume fraction of the dispersed zeolite phase, is the permeability

of the continuous polymer phase and is the permeability of the dispersed zeolite

phase.